What is 'normal' hair?

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What is ‘normal’ hair? Expert Rev. Dermatol. 3(4), 421–423 (2008)

Adriana Rakowska Department of Dermatology, CSK MSWiA, Woloska 137, 02-507 Warsaw, Poland Tel.: +48 022 824 2200 Fax: +48 022 824 2200 [email protected]

Lidia Rudnicka Author for correspondence

Department of Dermatology, CSK MSWiA, Woloska 137, 02-507 Warsaw, Poland Tel.: +48 022 824 2200 Fax: +48 022 824 2200 [email protected]

“New hair-imaging techniques have broadened our knowledge regarding normal hair and hair diseases.” New imaging techniques broaden the spectrum of hair diseases

New hair-imaging techniques have broadened our knowledge regarding normal hair and hair diseases. Trichoscopy, a new ancillary method for diagnosis of hair loss that uses dermoscopy or videodermoscopy of hair, scalp, eyebrows and eyelashes, allows the visualization and measurment of hair at high magnification without the need for plucking hair for light microscopic examination. The fi rst use of dermoscopy for visualization of scarring in spotted cicatricial alopecia dates back to the early 1990s [1] , but the method only gained popularity in recent years. In 2004, Lacrubba et al. first described videodermoscopic features of alopecia areata [2] . In 2005 and 2006, Rudnicka and Olszewska first used videodermoscopy for the evaluation of disease severity in androgenic alopecia and for monitoring treatment efficacy [3] . In 2006, Ross et al. specified videodermoscopy features of different acquired hair and scalp diseases [4] . In 2006, the term ‘trichoscopy’ for hair and scalp videodermoscopy in hair loss diagnostics was first used [5] .

“…limited hair-shaft diameter heterogeneity is a normal finding and does not have to indicate hair miniaturization…” Since then, several trichoscopic hair and scalp abnormalities have been described and trichoscopy criteria for diagnosing female androgenic alopecia developed. Interestingly, ‘normal’ hair trichoscopy was not described until very recently [101] . Normal hair thickness

Our results have shown that hair thickness may differ between scalp areas in the same person. Our studies have shown www.expert-reviews.com

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that mean hair thickness was 0.061 mm in the frontal area versus 0.058 mm in the occipital area in healthy individuals. This difference was statistically significant. Hair thickness in the temporal areas represented a value that was lower than the frontal area and higher than the occipital area. Differences between the left and right temporal area were statistically not significant. The mean proportion of thin (0.05 mm) hairs was approximately 6, 21 and 73% in healthy Caucasian females, respectively [101] , indicating that a limited hair-shaft diameter heterogeneity is a normal finding and does not have to indicate hair miniaturization, a characteristic feature of androgenic alopecia [6] . Pilosebaceous units

Hairs usually grow in small groups, growing from one follicular orifice. It has been shown that these are usually single-hair, double-hair or triple-hair units. Units of four hairs or more are rare and account for less than 5% of all hair units. Units of five or more hairs are usually not seen in normal individuals. We have seen units of up to eight hairs in tufted folliculitis. Follicular ostia

Trichoscopy allows the observation of follicular ostia and perifollicular skin at multiple magnification. Numerous abnormalities, such as white dots (scarring hair follicles), black dots (cadaverized hair) and yellow dots (probably of various origins), have been described. According to Tosti’s group, yellow dots correspond to degenerated follicular keratinocytes and sebum contained within the dilated ostium of nanogen and miniaturized hair follicles and are found exclusively in alopecia areata and

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advanced male androgenic alopecia [7] . We do not agree fully with this opinion. We see yellow dots regularly in female androgenic alopecia and have suggested that yellow dots in these patients result from the presence of sebaceous lobules, which, in histopathology, appear large in relation to the miniaturized follicles. We hypothesized that these sebaceous glands are still active after advanced hair follicle miniaturization and produce sebum, which creates intraepidermal sebum lagoons. These sebum lagoons appear as yellow dots in trichoscopy. We believe that yellow dots may be characteristic of a wide spectrum of hair diseases and may also represent a wider spectrum of histopathological appearances of follicle ostia and infundibula than previously anticipated. Regardless of this discrepancy in opinions, it should be emphasized that the ability to visualize hair follicle ostia enabled the identification of new or newly described diseases, for example, alopecia areata incognita. This disease, described recently in detail, is a variety of alopecia areata characterized by acute diffuse shedding of telogen hairs in the absence of typical patches. Clinically, it has features of telogen effluvium or androgenic alopecia [7] . This example shows that trichoscopy enables diagnosis of diseases that may have remained undiagnosed without this method. Hair structure

Hair-shaft abnormalities encompass a group of congenital or acquired alterations that involve the hair shaft. They usually lack macroscopic features, which would enable easy diagnosis in medical practice. Thus, the usual diagnostic method is light microscopy. Diseases that may be diagnosed by light microscopy include Netherton syndrome, monilethrix, woolly hair syndrome, pili torti and pili annulati.

“…trichoscopy enables diagnosis of diseases that may have remained undiagnosed without this method.” The first case that showed the value of trichoscopy in diagnosing hairs shaft abnormalities was published in 2006 [8] . This was a case of a 44-year-old woman with negative family history for genetically inherited disorders, who reported a life-long history of thin, short and fragile hair, but with no significant hair loss. In this patient, trichoscopy demonstrated an unusual picture of hair shafts with a beaded appearance, bent regularly at multiple locations with a tendency to curve in different directions, giving it an appearance of a regularly bended ribbon. Based on this trichoscopy finding the diagnosis of monilethrix appeared obvious. In this patient, trichoscopy allowed the establishment of the diagnosis of monilethrix, which would probably have References 1

Kossard S, Zagarella S. Spotted cicatricial alopecia in dark skin. A dermoscopic clue to fibrous tracts. Australas. J. Dermatol. 34, 49–51 (1993).

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remained undiagnosed without this method as it was not clinically apparent that plucking hairs for light microscopy would be of diagnostic benefit.

“Trichoscopy is likely to increase the spectrum of defined hair and scalp diseases and it will probably increase the number of patients leaving dermatology offices with a clear diagnosis of a hair abnormality.” In such cases, despite characteristic microscopic findings, the diseases are not simple to diagnose in dermatological practice. Several hairs have to be plucked for microscopic evaluation, as usually not 100% of hairs are affected. Furthermore, affected hairs are typically shorter and more fragile, making them more difficult to sample. This is especially true for Netherton syndrome. Often, samples of hundreds of hairs are not sufficient to find the characteristic features of trichorrhexis invaginata in children suffering from suspected of Netherton syndrome. As shown by Rakowska et al., trichoscopy allows the easy identification of characteristic trichorhexis nodosa and golf tee-like features in both scalp hairs and eyebrows [9] . In woolly hair syndrome the term ‘woolly hair’ refers to an abnormal variant of fine, tightly curled hair that often exhibits decreased pigmentation. Before trichoscopy, distinguishing woolly hair from curly hair required evaluation of hair shafts by either light or electron microscopy. It was shown that trichoscopy can easily distinguish between healthy curly hair and the woolly hair syndrome [9] . The study by Rakowska et al. has shown that trichoscopy of monilethrix, pili torti, pili anulati and woolly hair provides comparable results to microscopic examination and has the benefit of being quick, easy and patient friendly [9] . Only in the case of trichotiodystrophy is trichoscopy insufficient for diagnosis. What now?

Trichoscopy is likely to increase the spectrum of defined hair and scalp diseases and it will probably increase the number of patients leaving dermatology offices with a clear diagnosis of a hair abnormality. However, it remains uncertain how fast this diagnostic progress in trichology will be followed by new therapeutic possibilities.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.

Lacarrubba F, Dall’Oglio F, Rita Nasca M et al. Videodermatoscopy enhances diagnostic capability in some forms of hair loss. Am. J. Clin. Dermatol. 5, 205–208 (2004).

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Olszewska M, Rudnicka L. Effective treatment of female androgenic alopecia with dutasteride. J. Drugs Dermatol. 4, 637–640 (2005).

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Ross EK, Vincenzi C, Tosti A. Videodermoscopy in the evaluation of hair and scalp disorders. J. Am. Acad. Dermatol. 55, 799–806 (2006).

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Rudnicka L, Olszewska M, Majsterek M et al. Presence and future of dermoscopy, Expert Rev. Dermatol. 1(6), 769–772 (2006).

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Messenger AG, Sinclair R. Follicular miniaturization in female pattern hair loss: clinicopathological correlations. Br. J. Dermatol. 155, 926–930 (2006).

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Tosti A, Whiting D, Iorizzo M et al. The role of scalp dermoscopy in the diagnosis of alopecia areata incognita. J. Am. Acad.

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Dermatol. DOI: 10.1016/j. jaad.2008.03.031 (2008) (Epub ahead of print). 8

Rakowska A, Slowinska M, Czuwara J, Olszewska M, Rudnicka L. Dermoscopy as a tool for rapid diagnosis of monilethrix. J. Drugs Dermatol. 6, 222–224 (2007).

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Rakowska A, Slowinska M, KowalskaOledzka E, Rudnicka L. Trichoscopy in hair shaft abnormalities. J. Dermatol. Case Rep. DOI:10.3315/jdcr/2008.1009 (2008) (Epub ahead of print).

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Rakowska A, Slowinska M, KowalskaOledzka E, Olszewska M, Rudnicka L. Trichoscopy criteria for diagnosing female androgenic alopecia. Nature Precedings (2006) http://hdl.handle.net/10101/ npre.2008.1913.1

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